As the feature size of metal oxide semiconductor field-effect transistors (MOSFETs) continues to decrease, short channel effects have become a critical design issue due to the reduction in size of the gate length. Fin Field-effect transistors (FinFET) exhibit excellent gate controllability on channel charge and superior electrostatic control capability, so that the feature size of complementary metal oxide semiconductor (CMOS) devices can be further reduced, such as process nodes below 20 nm.
Bipolar junction transistors (BJTs) are one of the most widely used semiconductor devices. A BJT can be implemented by a MOSFET manufacturing process.
The present inventor has discovered that, in the formation of the BJT by the conventional FinFET manufacturing process, etching the fin of a FinFET device may cause defects to the sides of the fin, resulting in a relatively high leakage current. Furthermore, since the emitter of the BJT is in the middle or at the bottom of the fin, the emitter has a relatively smaller surface area, so that the BJT has poor linearity.
As shown in FIG. 1, the area of the emitter (denoted by a dotted circle) is relatively small and the emitter junction may be affected by defects at the fin, so that a thus formed BJT has poor linearity. Furthermore, because each emitter junction area of the fins is relatively small, and the number and distribution of defects are different, resulting in different electric characteristics of the fins and poor uniformity of the electric characteristics of each fin. In actual applications, more than two BJT devices are used together. However, because the fins have different electric characteristics, the respective BJT devices also have different electrical characteristics, resulting in a mismatch of the BJT devices.
Thus, there is a need to provide a novel Fin-type bipolar semiconductor device and manufacturing method thereof to overcome the above-described deficiencies.